ggglimpopo: sorry, missed this thread til now.
Firstly - I was 43 when i had DS, and he DOES actually have a bit of a disability, but i am absolutely certain that my brimming, confident, happy little boy would not consider me selfish for having him!!!! (and it can't be determined whether my age was a factor, anyway).
Secondly, I have worked with lots of DS young people, and like you, my own impulse would not be to feel that DS was a reason not to have a child. Advances and education have changed life for DS children irrecognisably from what it was half a generation ago.
BUT we did have amnio when DS's leg was spotted at the 20 week scan, because there were factors which COULD have been indicators of far more severe chromosomal problems - as Marina talks of.
What I found really useful in knowing about my DS's leg before he was born was that I had done the research, found the parents suport sites, and was practically and emotionally prepared, and it had become more of an ordinary fact of life by the time he was born - so all that i had left to do was celebrate and get to know him.
But we didn't need to do amnio to find out about his leg - so I don't know if that pre-knowledge would have been worth a 200 in 1 chance of mc fromthe test. (I think it depends a lot on the skill and experience of the individual carrying it out).
How are you feeling?